From 2268169c14e5f00377512932cf2b7bc78e4577ad Mon Sep 17 00:00:00 2001 From: Vasily Gorbik Date: Thu, 24 Feb 2022 16:43:23 +0100 Subject: [PATCH] s390: remove unused expoline to BC instructions This reverts commit 6deaa3bbca80 ("s390: extend expoline to BC instructions"). Expolines to BC instructions were added to be utilized by commit de5cb6eb514e ("s390: use expoline thunks in the BPF JIT"). But corresponding code has been removed by commit e1cf4befa297 ("bpf, s390x: remove ld_abs/ld_ind"). And compiler does not generate such expolines as well. Compared to regular expolines, expolines to BC instructions contain displacement and all possible variations cannot be generated in advance, making kpatch support more complicated. So, remove those to avoid future usages. Acked-by: Heiko Carstens Acked-by: Sumanth Korikkar Signed-off-by: Vasily Gorbik --- arch/s390/include/asm/nospec-insn.h | 57 ----------------------------- arch/s390/kernel/nospec-branch.c | 25 +++---------- 2 files changed, 5 insertions(+), 77 deletions(-) diff --git a/arch/s390/include/asm/nospec-insn.h b/arch/s390/include/asm/nospec-insn.h index 0033dcd663b1..c419c9e87265 100644 --- a/arch/s390/include/asm/nospec-insn.h +++ b/arch/s390/include/asm/nospec-insn.h @@ -35,18 +35,10 @@ _LC_BR_R1 = __LC_BR_R1 __THUNK_PROLOG_NAME __s390_indirect_jump_r\r2\()use_r\r1 .endm - .macro __THUNK_PROLOG_BC d0,r1,r2 - __THUNK_PROLOG_NAME __s390_indirect_branch_\d0\()_\r2\()use_\r1 - .endm - .macro __THUNK_BR r1,r2 jg __s390_indirect_jump_r\r2\()use_r\r1 .endm - .macro __THUNK_BC d0,r1,r2 - jg __s390_indirect_branch_\d0\()_\r2\()use_\r1 - .endm - .macro __THUNK_BRASL r1,r2,r3 brasl \r1,__s390_indirect_jump_r\r3\()use_r\r2 .endm @@ -89,23 +81,6 @@ _LC_BR_R1 = __LC_BR_R1 .endif .endm - .macro __DECODE_DRR expand,disp,reg,ruse - .set __decode_fail,1 - .irp r1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 - .ifc \reg,%r\r1 - .irp r2,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15 - .ifc \ruse,%r\r2 - \expand \disp,\r1,\r2 - .set __decode_fail,0 - .endif - .endr - .endif - .endr - .if __decode_fail == 1 - .error "__DECODE_DRR failed" - .endif - .endm - .macro __THUNK_EX_BR reg,ruse # Be very careful when adding instructions to this macro! # The ALTERNATIVE replacement code has a .+10 which targets @@ -126,42 +101,17 @@ _LC_BR_R1 = __LC_BR_R1 555: br \reg .endm - .macro __THUNK_EX_BC disp,reg,ruse -#ifdef CONFIG_HAVE_MARCH_Z10_FEATURES - exrl 0,556f - j . -#else - larl \ruse,556f - ex 0,0(\ruse) - j . -#endif -556: b \disp(\reg) - .endm - .macro GEN_BR_THUNK reg,ruse=%r1 __DECODE_RR __THUNK_PROLOG_BR,\reg,\ruse __THUNK_EX_BR \reg,\ruse __THUNK_EPILOG .endm - .macro GEN_B_THUNK disp,reg,ruse=%r1 - __DECODE_DRR __THUNK_PROLOG_BC,\disp,\reg,\ruse - __THUNK_EX_BC \disp,\reg,\ruse - __THUNK_EPILOG - .endm - .macro BR_EX reg,ruse=%r1 557: __DECODE_RR __THUNK_BR,\reg,\ruse .pushsection .s390_indirect_branches,"a",@progbits .long 557b-. .popsection - .endm - - .macro B_EX disp,reg,ruse=%r1 -558: __DECODE_DRR __THUNK_BC,\disp,\reg,\ruse - .pushsection .s390_indirect_branches,"a",@progbits - .long 558b-. - .popsection .endm .macro BASR_EX rsave,rtarget,ruse=%r1 @@ -173,17 +123,10 @@ _LC_BR_R1 = __LC_BR_R1 #else .macro GEN_BR_THUNK reg,ruse=%r1 - .endm - - .macro GEN_B_THUNK disp,reg,ruse=%r1 .endm .macro BR_EX reg,ruse=%r1 br \reg - .endm - - .macro B_EX disp,reg,ruse=%r1 - b \disp(\reg) .endm .macro BASR_EX rsave,rtarget,ruse=%r1 diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c index 60e6fec27bba..c302e0a7d38f 100644 --- a/arch/s390/kernel/nospec-branch.c +++ b/arch/s390/kernel/nospec-branch.c @@ -105,6 +105,7 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) s32 *epo; /* Second part of the instruction replace is always a nop */ + memcpy(insnbuf + 2, branch, sizeof(branch)); for (epo = start; epo < end; epo++) { instr = (u8 *) epo + *epo; if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04) @@ -125,34 +126,18 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end) br = thunk + (*(int *)(thunk + 2)) * 2; else continue; - /* Check for unconditional branch 0x07f? or 0x47f???? */ - if ((br[0] & 0xbf) != 0x07 || (br[1] & 0xf0) != 0xf0) + if (br[0] != 0x07 || (br[1] & 0xf0) != 0xf0) continue; - - memcpy(insnbuf + 2, branch, sizeof(branch)); switch (type) { case BRCL_EXPOLINE: + /* brcl to thunk, replace with br + nop */ insnbuf[0] = br[0]; insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); - if (br[0] == 0x47) { - /* brcl to b, replace with bc + nopr */ - insnbuf[2] = br[2]; - insnbuf[3] = br[3]; - } else { - /* brcl to br, replace with bcr + nop */ - } break; case BRASL_EXPOLINE: + /* brasl to thunk, replace with basr + nop */ + insnbuf[0] = 0x0d; insnbuf[1] = (instr[1] & 0xf0) | (br[1] & 0x0f); - if (br[0] == 0x47) { - /* brasl to b, replace with bas + nopr */ - insnbuf[0] = 0x4d; - insnbuf[2] = br[2]; - insnbuf[3] = br[3]; - } else { - /* brasl to br, replace with basr + nop */ - insnbuf[0] = 0x0d; - } break; } -- 2.34.1